Association of TRPV5 gene polymorphism with calcium urolithiasis: a case-control study from West Bengal, India

Homozygous GRHPR C.494G>A mutation is deleterious that causes early onset of nephrolithiasis in West Bengal, India

Pediatric nephrolithiasis (NL) or Kidney stone disease (KSD) is an untethered topic in Asian population. In Western countries, the annual incidence of paediatric NL is around 6-10%. Here, we present data from West Bengal, India, on lower age (LA, 0-20 years) NL and its prevalence for the first time. To discover the mutations associated with KSD, twenty-four (18 + 6) rare LA-NL patients were selected for Whole Exome Sequencing (WES) and Sanger sequencing, respectively. It was found that GRHPR c. 494G>A mutation (MZ826703) is predominant in our study cohort. This specific homozygous mutation is functionally studied for the first time directly from human peripheral mononuclear cell (PBMC) samples. Using expression study with biochemical activity and computational analysis we assumed that the mutation is pathogenic with loss of function. Moreover, three genes, AGXT, HOGA1 and GRHPR with Novel variants known to cause hyperoxaluria were found frequently in the study cohort. Our study analyses the genes and variations that cause LA-NL, as well as the molecular function of the GRHPR mutation, which may serve as a clinical marker in the population of West Bengal, Eastern India.

Metabolic and Genetic Evaluation in Children with Nephrolithiasis

OBJECTIVE

To evaluate metabolic and genetic abnormalities in children with nephrolithiasis attending a referral center in North India.

METHODS

The patients aged 1-18 y old with nephrolithiasis underwent biochemical evaluation and whole-exome sequencing. The authors evaluated for monogenic variants in 56 genes and compared allele frequency of 39 reported polymorphisms between patients and 1739 controls from the GenomeAsia 100 K database.

RESULTS

Fifty-four patients, aged 9.1 ± 3.7 y were included. Stones were bilateral in 42.6%, familial in 33.3%, and recurrent in 25.9%. The most common metabolic abnormalities were hypercalciuria (35.2%), hyperoxaluria (24.1%), or both (11.1%), while xanthinuria (n = 3), cystinuria (n = 1), and hyperuricosuria (n = 1) were rare. Exome sequencing identified an etiology in 6 (11.1%) patients with pathogenic/likely pathogenic causative variants. Three variants in MOCOS and one in ATP7B were pathogenic; likely pathogenic variants included MOCOS (n = 2), AGXT, and SLC7A9 (n = 1, each). Causality was not attributed to two SLC34A1 likely pathogenic variants, due to lack of matching phenotype and dominant family history. Compared to controls, allele frequency of the polymorphism TRPV5 rs4252402 was significantly higher in familial stone disease (allele frequency 0.47 versus 0.53; OR 3.2, p = 0.0001).

CONCLUSION

The chief metabolic abnormalities were hypercalciuria and hyperoxaluria. A monogenic etiology was identified in 11% with pathogenic or likely pathogenic variants using a gene panel for nephrolithiasis. Heterozygous missense variants in the sodium-phosphate cotransporter SLC34A1 were common and required evaluation for attributing pathogenicity. Rare polymorphisms in TRPV5 might increase the risk of familial stones. These findings suggest that a combination of metabolic and genetic evaluation is useful for determining the etiology of nephrolithiasis.

Association of TRPV5, CASR, and CALCR genetic variants with kidney stone disease susceptibility in Egyptians through main effects and gene–gene interactions

Kidney stone disease (KSD) represents an urgent medical problem because of increasing its prevalence. Several functional polymorphisms in genes involved in the renal handling of calcium were associated with KSD pathogenesis. Among those, the rs4236480 of transient receptor potential vanilloid member 5 (TRPV5) gene, the rs1801725 of calcium-sensing receptor (CASR) gene, and the rs1801197 of calcitonin receptor (CALCR) gene appear to be of great importance. Due to the scarce data on the Egyptians, this study aimed to evaluate the association of these candidate genetic variants with the risk of developing KSD in an Egyptian population. To do so, the biochemical parameters were measured along with the genotyping of the three polymorphisms using allelic discrimination assay in 134 KSD patients and 86 age and sex-matched healthy subjects. The results showed that the genotypic distributions and allelic frequencies of the studied variants were significantly different between cases and controls. The three polymorphisms increased the risk of KSD significantly under all the tested genetic models (OR ranges from 2.152 to 5.994), except for the recessive model of the CALCR rs1801197 polymorphism after Bonferroni correction. The gene–gene interaction analyzed by multifactor dimensionality reduction selected the three-locus combination as the best model associated with the susceptibility to KSD with OR 9.706. Further, synergistic interactions were identified between TRPV5 rs4236480 and CALCR rs1801197 variants and CASR rs1801725 and CALCR rs1801197 variants. In conclusion, the TRPV5 rs4236480, CASR rs1801725, and CALCR rs1801197 polymorphisms showed a significant association with the risk of KSD in the Egyptian population. Furthermore, their complex interactions might have an impact on the genetic susceptibility to develop KSD.